Modern farming techniques often rely on efficiency of scale for survival and profitability. In one example, animal raising and feeding is often done at a central facility having a large number of animals. Chickens, turkeys, pigs, and cows are often housed at a large facility, with the resulting generation of large quantities of manure. This manure is collected and stored. The manure storage pit may be quite large in some instances. Some storage pits or lagoons are about 800 feet long, 250 feet wide, about 20 feet deep, and can hold about 30 million gallons of manure.
The manure may ultimately be spread onto a field for two reasons: first, to dispose of the manure, and second, to apply fertilizer to the field. The manure is often applied only in the spring and fall in some regions. The manure is often not spread when it either will not be absorbed or cannot be applied because of the presence of crops. The manure is thus held for a long time period of several months.
At appropriate times, the manure is spread on the fields. While it is possible for a single farm to invest in the specialized equipment, and to use this equipment only twice a year, this is often not done. Instead, service providers buy the equipment and travel from site to site, pumping out the manure lagoons onto the fields.
This is often done by positioning a floating barge or dredge on the lagoon surface, and coupling the moving barge to the lagoon edge using a floated hose or pipe of some sort. Sometimes the hose or pipe empties into a storage tank. In other systems, the same hose or pipe, or a different hose or pipe, can continue from the lagoon to a tractor pulling a manure tillage injector or sprayer. The tractor can travel back and forth over the fields, with the hose trailing behind, spreading the manure on the fields. The hose length may be on the order of a mile. So-called “lay-flat” hose is currently used. Lay-flat hose lies flat when not pressurized, rather than remain round. A hard hose that remains round is also used. The manure distribution is also accomplished by pumping the manure into a tank, which may then be pulled behind a tractor and the manure spread onto or into the field. Manure distribution is further described in commonly assigned U.S. Pat. No. 6,427,612, herein incorporated by reference.
In a related use, industrial or municipal sludge can also be disposed of on, or into, a field. Such sludge is typically the sludge left over from wastewater processing. The wastewater may be municipal wastewater or wastewater from a processing plant, for example a food processing plant, that may be disposed of on a field. As used herein, the term “sludge” refers to both manure and wastewater sludge, both having a sufficient amount of liquid to allow for pumping the sludge.
Whether using a drag hose system or a tank system, it is normally desirable to apply the sludge evenly over the fields. If too much sludge is applied in an area, it may not be absorbed in to the ground, and may result in run-off. Too much sludge in one spot may also be harmful to crop plants growing there. Excessive sludge may also not be utilized by plants, with nitrates ending up in the ground water, an undesirable situation.
Too little sludge is also undesirable, as crops dependent on the sludge for fertilizer may receive little or no fertilizer. Crop roots typically reach only about the extent of the canopy, and no further. Thus, an acceptable “average” sludge distribution consisting of alternating high and low areas along a crop row may result in unacceptable variations in crop growth. Even sludge distribution is therefore important for crop production and environmental issues.
Sludge distributors or manifolds are often found carried near the tanks or at the end of the drag hoses. Examples of such sludge distributors are made by Vogelsang (Hugo Vogelsang Maschinenbau GmbH, Holthöge 10-14, D-49632 Essen/OI.) (www.vogelsang-gmbh.com), under the DOSIMAT, DOSICUT, AND EXACUT brand names. The distributors are distributed by Vogelsang USA (Twinsburg Ohio).
The distributors are often selected for a limited pressure and flow range. Specifically, the pressure delivered by a pump from a tank or from the manure lagoon is known or estimated, and the proper distributor selected. Many current distributors were developed for use with tanks, and are now used with drag hose systems. The proper selection of a sludge distributor is important. If the backpressure built up within the distributor drops too low, then uneven sludge distribution will likely result. If the backpressure becomes too high, then the sludge distribution may be even, but much energy is wasted.
In one example, a distributor may be initially installed for a range of 400-600 GPM, but a range of 1200-1400 GPM may later be desired. It might be possible to meet this higher range, but at the cost of significantly higher pressure and the resultant energy wastage. The range of flow rates expected through hose drag systems can be large, from 200-1600 GPM. These large ranges are difficult to achieve without either wasting energy to maintain a large backpressure or dropping too low to insure even distribution.
Applicant believes that current systems address this problem by replacing the entire distributor, or operating using the initial distributor with large backpressure or uneven flow.
What would be desirable is a system for delivering sludge to multiple hoses at an even flow rate; with little excess back pressure, over a large range of flow rates.